Page 470 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Gas Turbines 447

pendent upon the specific circumstances. As a general rule, the more
units operated and the more time in operation the further down the list the
user progresses. Although there are still users who find an OEM mainte-
nance contract attractive, as they gain more experience users tend to seek
more direct involvement in their gas turbine maintenance.
In refineries and chemical process plants, unscheduled shutdowns can
be extremely expensive. Therefore, turbines are generally maintained at
a high level by experienced personnel employing sophisticated condition
monitoring and corrective maintenance techniques. By contrast, some
standby electrical generator and crude oil transmission installations are
maintained at a very low level and have effectively no maintenance pro-
cedures beyond contacting the manufacturer’s representative when the
equipment fails to start or operate. The majority of the gas turbine equip-
ment operating is maintained at a level somewhere between these ex-
tremes. The operating availability and reliability is directly related to the
level and quality of maintenance performed.2
A maintenance policy which realistically addresses the costs involved
in outages, spare parts, and engineering services should be developed as
early as possible in order to select the level of maintenance which is
suited to the application. Ideally this policy should be adopted before a
gas turbine is selected and should form an integral part of the driver se-
lection. Most maintenance managers unless specifically experienced in
gas turbines are not capable of realistically setting this type of policy. It
should determine the level of support to be provided to ensure that corpo-
rate objectives can be fulfilled. It should establish goals and provide
guidelines as to what is practical, reliable, and economical based on the
operating and availability requirements of the turbine.2
The setting of such a policy may be facilitated by a competent outside
consultant if such an individual is not available within the user’s com-
pany. Primary emphasis should be placed on ensuring that personnel with
the right skills are available, or that the people who are available receive
the necessary training.
Along with a maintenance policy or a part of it the objectives of
planned maintenance should be defined and their relative importance de-
termined. It is difficult to define the objectives of planned maintenance,
but in general they can be summarized as follows:

1. Minimize capital investment.
2. Maximize turbine reliability and availability.
3. Minimize operating and maintenance costs.
4. Maintain original design performance.
5. Incorporate appropriate product design improvements .’